Table 3.

Calorimetric values of enthalpy and entropy of renaturation for the 22AG oligo and its O- and U-derivatives

Oligo	$T_{\text{m}}^{\text{cal}}$ (°C)	ΔHcal (kcal mol−1)	ΔScal (kcal mol−1 K−1)
22AG	64	−41.5a	−0.123
22AG-O	66	−23.5	−0.069
22AG-U	63	−33.2	−0.097

For the DSC experiments, the oligos were prepared at ∼50–70 μM strand concentration in 10 mM sodium cacodylate buffer at pH 7.0 containing 100 mM KCl. Calorimetric values of ΔH_cal and ΔS_cal for the reversible thermal transitions were obtained by the DSC profiles (variation of heat capacity versus temperature), using the Cp-Calc software.

^aComparison between the ΔH_VH (−45.0 kcal mol⁻¹) and the ΔH_cal (−41.5 kcal mol⁻¹) for the thermal renaturation of the 22AG oligo gave a ratio n of ∼1 (n = 1.08). This confirmed the monomolecularity of the process and the validity of the two-state transition model assumed in the Van't Hoff analysis.